| Bias | Author's judgement | Support for judgement |
| Confounding |
Serious |
Comment: The following review confounders (Age, Gender) some comorbidities but severity, obesity, immunosuppression were not controlled. The baseline characteristics presented are measured but not adjusted. Comorbidities at baseline are unbalanced at baseline but were controlled for like ethnicity nor immunosuppression. |
| Selection of participants into the study |
NI |
Comment: It is unclear whether start of the intervention co-incided with start of follow up (hospital admission). Quote: "From February 1, 2020 to April 4, 2020, a total of 550 critically ill COVID-19 patients were admitted to Tongji Hospital, including 344 males and 206 females. The median age was 68 years old. Forty-eight patients received HCQ treatments (Shanghai Pharmaceutical CO., LTD, 200 mg/tablet) (oral 200 mg twice per day for 710 days), and the remaining 502 received basic treatments (non-hydroxychloroquine treatments, NHCQ).". |
| Intervention classification |
Low |
Comment: Data were collected from electronic health records, and treatment groups were classified using clearly defined criteria. Quote: "Health care data of COVID-19 patients, including medical history, chest CT, and laboratory tests, in-hospital therapies, and clinical deposits (death or cured discharge), were extracted by data coordinators through the electronic medical records.". |
| Deviation from intended intervention |
Moderate |
Comment: There is an imbalance between experimental arms for reported co- interventions antibiotics, and interferon but not for other antivirals and immunoglobulin. |
| Missing data |
Low |
Comment: No participants were excluded due to missing data. |
| Measurements of outcomes |
Low |
Comment: Observer-reported objective outcome (death). |
| Selection of the reported results |
Moderate |
Comment: The outcomes and analyses are clearly defined in the methods section. There is no a priori registered protocol or statistical analysis plan available. |